A semiconductor wafer may be subjected to a chemical vapor deposition process such as an epitaxial deposition process to grow a thin layer of silicon on the front surface of the wafer. This process allows devices to be fabricated directly on a high quality epitaxial layer. Conventional epitaxial deposition processes are disclosed in U.S. Pat. Nos. 5,904,769 and 5,769,942, which are incorporated herein by reference.
The semiconductor wafer is transferred to (i.e., loaded) and removed from (i.e., unloaded) a deposition chamber using a quartz carrier blade. A conventional quartz carrier blade has spaced, arcuate ledge surfaces that are recessed below a top surface of the blade. The ledge surfaces have descending sides that fall off perpendicular to the ledge surface resulting in sharp edges. These “sharp” edges underlie the back side of the support semiconductor wafer.
The loading temperature of the deposition chamber is about 700° C. and the unloading temperature is about 800° C. The wafer and the carrier blade are at a lower temperature when the wafer is loaded into the relatively hot deposition chamber. As a result of this temperature difference, the wafer experiences thermal shock as it enters the deposition chamber. The wafer also experiences thermal shock when the carrier blade unloads the wafer from the chamber because the blade is at about room temperature and the wafer is at about 800° C. The wafer tends to bow downwards during the thermal shock, and the sharp edges of the blade between the ledge surfaces and the sides cause scratches and other damage to the back side of the bowing wafer.